484 THE POPULAR SCIENCE MONTHLY 



The only series of data for hair color in husband and wife (where 

 one may not suspect artificial selection of cases) is that given by Mr. 

 Galton-'' for the parents of English scientific men. I have grouped his 

 data into three classes, and calculated the coefficient of mean square con- 

 tingency, which is -|- .34. No stress is to be laid on the result, since the 

 number of cases is small and the coarse grouping — which is necessary 

 if the constant is to be calculated at all — unsatisfactory. 



4. Physical Defects and Pathological Conditions 



To Alexander Graham BelP^ probably belongs the credit of first 

 laying great stress upon the social consequences of assortative mating. 

 The title of his memoir, " Upon the Formation of a Deaf Variety of 

 the Human Race," sufficiently indicates the seriousness with which he 

 regarded the intermarriage of the deaf. 



Probably assortative mating for deafness is more nearly perfect than 

 that for any other known character. The reasons for this are patent. 

 Hearing individuals rarely choose non-hearing mates. When both 

 partners are deaf, on the other hand, they are united by the strong bond 

 of fellowship and sympathy growing out of their similar condition, they 

 communicate with each other with perfect ease and freedom, and the 

 social interests and sympathies outside their own home are the same. 



The extensive records given by Fay^^ rather than those used by 

 Bell in his pioneer study may furnish illustrations. 



Table III. shows that in the marriages of the deaf, 72.5 per cent. 



TABLE III 



Marriages of the Deaf Number Percentage 



Both partners deaf 3,242 72.512 



One partner deaf ; the other hearing 894 19.995 



One partner deaf ; the other unreported whether deaf or hearing. 335 7.493 



Total 4,471 100.000 



have both of the contracting parties deaf as contrasted with 20 per cent. 

 in which one is deaf and the other a hearing person. When we consider 

 that in the general population of the United States there are roundly 

 1,500 hearing persons to one deaf, and consequently about 1,500 hearing 

 persons to one deaf from whom a given deaf individual might seek to 

 select a life partner, we see to what enormous extent sexual selection is 

 at work for this character.'® 



^•Galton, F., "English Men of Science," p. 21, 1895. 



*'Bell, A. G., Mem. Nat. Acad. Sci., Vol. 2, pp. 179-262, 1883. 



**Fay, E. A., "Marriages of the Deaf in America," Washington (Volta 

 Bureau), 1898. 



=" Schuster (Biometril-a, Vol. 4, p. 473, 1906) was unable to calculate the 

 precise intensity of the assortative mating coefficients for deafness because of the 

 mathematical difficulties involved, but it is certainly considerably higher than 

 + .90. 



